A381574 G.f. A(x) satisfies A(x) = 1/(1 - x*A(x*A(x)))^3.

1, 3, 15, 118, 1206, 14712, 204385, 3143826, 52580328, 944416084, 18056415144, 365065244238, 7765839784508, 173123253590079, 4031536347783786, 97807655876704029, 2466489368705170539, 64527021089110890192, 1748298996924574135699, 48982266056400514509660

Offset: 0

Author

Seiichi Manyama, Feb 28 2025

Keywords

• nonn

Crossrefs

Column k=1 of A381573.

Cf. A381570, A381615.

Programs

PARI

a(n, k=1) = if(k==0, 0^n, 3*k*sum(j=0, n, binomial(3*n-2*j+3*k, j)/(3*n-2*j+3*k)*a(n-j, j)));

Formula

See A381573.

G.f.: B(x)^3, where B(x) is the g.f. of A381615.